1. Field of the Invention
The invention relates generally to semiconductor sensors and more particularly to a pressure measurement apparatus including a housing enclosing a semiconductor pressure transducer.
2. Description of the Related Art
Semiconductor pressure transducers ordinarily are enclosed within a housing for protection against contamination. Oppositely facing surfaces of a diaphragm region of a semiconductor differential pressure transducer usually are isolated from each other within a housing to facilitate their exposure to distinct measurand environments for which a pressure difference is to be measured.
For example, one type of earlier semiconductor differential pressure transducer includes a diaphragm having at least one piezoresistor formed in it. A change in the differential pressure applied across oppositely facing surfaces of the diaphragm causes a change in the resistor value of the piezoresistor. The change in resistor value is approximately proportional to the change in differential pressure. Thus, measurement of the resistor value can be used to determine the differential pressure applied across the diaphragm.
In practice, changes in an individual piezoresistor's value can be small and difficult to measure. Therefore, in a typical semiconductor diaphragm, four piezoresistors are formed in a Wheatstone Bridge configuration.
A pressure measurement apparatus of the general type described herein preferably is easily adaptable for use in a wide variety of applications. For example, such an apparatus can be used on a circuit board crowded with other electronic circuits. Thus, it should be compact and easy to use with a standard circuit board. Moreover, physical space limitations frequently can complicate coupling of a pressure measurement apparatus to tubing which communicates with one or more measurand environments. Therefore, the apparatus ought to be easy to couple to such tubing.
While earlier pressure measurement apparati generally have been acceptable, there have been shortcomings with their use. More specifically, earlier apparati generally have not provided the combination of sufficiently compact size plus adequate ease of coupling to tubing providing access to measurand environments. For example, one earlier type of pressure measurement apparatus includes a housing having two vent ports formed in it. The vent ports are formed in opposite sides of the housing. A semiconductor pressure transducer residing within the housing includes a diaphragm region which has two oppositely facing surfaces each exposed to one of the two vent ports. Unfortunately, coupling tubes to vent ports disposed on opposite sides of a housing can be somewhat difficult when the apparatus is connected to a crowded circuit board since the tubes must exit from opposite sides of the PC board.
Another earlier pressure measurement apparatus, while providing two vent ports formed in one side of its housing, suffers from other limitations. Its housing is relatively large and occupies a significant amount of space on a circuit board. Furthermore, the housing is formed from a combination of metallic and ceramic materials. Consequently, it can be relatively expensive to produce and can suffer from mechanical weakness at the juncture of the metallic and ceramic materials.
Pressure measurement apparati of the general type described herein ordinarily have been produced with electrical pin terminals in a Single-In-Line (SIP) configuration. There has been a need for an apparatus which provides pin terminals in a Dual-In-Line (DIP) configuration and which can be readily used in circuit boards utilizing surface mounting techniques.
Thus, there exists a need for a compact and durable pressure measurement apparatus which provides two vent ports in a single side of its housing, and which provides DIP pin terminals which are easily adaptable to surface mounting techniques. The present invention meets these needs.
Furthermore, in view of the wide range of environments in which such a pressure measurement apparatus can be used and the differing space limitations in such environments, it is desirable that the configuration of the vent ports formed in the housing be relatively easy and inexpensive to modify so as to meet specific user requirements. The invention meets this need as well.